5-HT1 receptor

In vitro activity: Rizatriptan Benzoate (also known as MK-462 Benzoate) is a brand-new, highly effective, and selective agonist at serotonin 5-HT1B and 5-HT1D receptors; it may be utilized to treat acute attacks of migraines.

Rizatriptan blocks the release of CGRP in anesthetized guinea pigs by acting on 5-HT(1D) receptors on perivascular trigeminal nerves, thereby inhibiting neurogenic vasodilation. In anesthetized guinea pigs, rizatriptan causes a brief decrease in dural blood vessel diameter, which returns to baseline levels in 10 minutes.[1] The dural plasma protein extravasation that results from intense electrical stimulation of the trigeminal ganglion is markedly inhibited by rizatriptan. In rats under anesthesia, ritariptan dramatically lowers electrically induced dural vasodilation.[2] It has been observed that Rizatriptan Benzoate can downregulate SP gene expression in the rat midbrain by significantly reducing SP mRNA levels in the midbrains of both normal and model group rats. In rat models of migraine, rizatriptan benzoate diminishes the analgesic effects of the endogenous pain modulatory system by significantly lowering midbrain PENK mRNA expression, which in turn lowers midbrain met-enkephalin and leu-enkephalin levels.[3] The number of Fos-like immunoreactive neurons in the caudal part and raphe magnus nucleus of the spinal trigeminal nucleus decreased in conscious rats, while the number increased in the periaqueductal gray and remained unchanged in the ventromedial hypothalamic and mediodorsal thalamus nuclei. These findings were observed in rats administered Riztriptan Benzoate.[4] Rizatriptan Benzoate significantly lowers the rats' head-flicking frequency. Additionally, compared to when treatment is not received, rizatriptan benzoate significantly shortens the duration of grooming behavior by almost two times. [5]

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These studies investigated the pharmacology of neurogenic dural vasodilation in anaesthetized guinea-pigs. Following introduction of a closed cranial window the meningeal (dural) blood vessels were visualized using intravital microscopy and the diameter constantly measured using a video dimension analyser. Dural blood vessels were constricted with endothelin-1 (3 microg kg(-1), i.v.) prior to dilation of the dural blood vessels with calcitonin gene-related peptide (CGRP; 1 microg kg(-1), i.v.) or local electrical stimulation (up to 300 microA) of the dura mater. In guinea-pigs pre-treated with the CGRP receptor antagonist CGRP((8-37)) (0.3 mg kg(-1), i.v.) the dilator response to electrical stimulation was inhibited by 85% indicating an important role of CGRP in neurogenic dural vasodilation in this species. Neurogenic dural vasodilation was also blocked by the 5-HT(1B/1D) agonist rizatriptan (100 microg kg(-1)) with estimated plasma levels commensurate with concentrations required for anti-migraine efficacy in patients. Rizatriptan did not reverse the dural dilation evoked by CGRP indicating an action on presynaptic receptors located on trigeminal sensory fibres innervating dural blood vessels. In addition, neurogenic dural vasodilation was also blocked by the selective 5-HT(1D) agonist PNU-142633 (100 microg kg(-1)) but not by the 5-HT(1F) agonist LY334370 (3 mg kg(-1)) suggesting that rizatriptan blocks neurogenic vasodilation via an action on 5-HT(1D) receptors located on perivascular trigeminal nerves to inhibit CGRP release. This mechanism may underlie one of the anti-migraine actions of the triptan class exemplified by rizatriptan and suggests that the guinea-pig is an appropriate species in which to investigate the pharmacology of neurogenic dural vasodilation.[1]

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These studies in anaesthetised rats showed, using intravital microscopy, that the novel anti-migraine agent, Rizatriptan, significantly reduced electrically stimulated dural vasodilation but had no effect on increases in dural vessel diameter produced by exogenous substance P or calcitonin gene-related peptide (CGRP). Rizatriptan also significantly inhibited dural plasma protein extravasation produced by high intensity electrical stimulation of the trigeminal ganglion. We suggest that rizatriptan inhibits the release of sensory neuropeptides from perivascular trigeminal nerves to prevent neurogenic vasodilation and extravasation in the dura mater. These prejunctional inhibitory effects may be involved in the anti-migraine action of rizatriptan.[2]

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The present study utilized a nitroglycerin-induced rat model of migraine to detect the effects of Rizatriptan benzoate on proenkephalin and substance P gene expression in the midbrain using real-time quantitative polymerase chain reaction and investigate whether rizatriptan benzoate can regulate the endogenous pain modulatory system. The results showed that rizatriptan benzoate significantly reduced expression of the mRNAs for proenkephalin and substance P. Rizatriptan benzoate may inhibit the analgesic effect of the endogenous pain modulatory system.[3]

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Fos expression in the brain was systematically investigated by means of immunohistochemical staining after electrical stimulation of the dura mater surrounding the superior sagittal sinus in conscious rats. Fos-like immunoreactive neurons are distributed mainly in the upper cervical spinal cord, spinal trigeminal nucleus caudal part, raphe magnus nucleus, periaqueductal gray, ventromedial hypothalamic nucleus, and mediodorsal thalamus nucleus. With the pre-treatment of intraperitoneal injection of Rizatriptan benzoate, the number of Fos-like immunoreactive neurons decreased in the spinal trigeminal nucleus caudal part and raphe magnus nucleus, increased in the periaqueductal gray, and remained unchanged in the ventromedial hypothalamic nucleus and mediodorsal thalamus nucleus. These results provide morphological evidence that the nuclei described above are involved in the development and maintenance of the trigeminovascular headache.[4]

SYBR green real-time quantitative PCR [3]
Twenty-microliter reactions comprised 10 μL of SYBR Premix Ex Taq™, 0.4 μL of upstream and downstream primers (10 μM), 0.4 μL of ROX Reference Dye, 2.0 μL of cDNA, and 6.8 μL of dH2O. Different concentrations of plasmid standard samples (1.2 × 103−1.2 × 109) copies/μL were processed by quantitative PCR. Each sample was run in triplicate. Reaction conditions were as follows: 94°C pre-denaturation for 2 minutes, 94°C denaturation for 30 seconds, 62°C annealing for 30 seconds, 72°C extension for 30 seconds, for a total of 40 cycles. Fluorescence signals were measured at the end of annealing in each cycle with the critical point for measurement defined during PCR amplification, i.e. the value of the threshold cycle corresponding to the inflection point of fluorescence signals entering the exponential growth phase above background level. A melting curve analysis was performed in a pattern of 95°C for 15 seconds, 60°C for 20 seconds, and 95°C for 15 seconds.

In preliminary experiments it was found that, following introduction of the cranial window, the dural blood vessels typically were observed to be maximally dilated, so that electrical stimulation of the cranial window produced little if any increase in diameter. It was therefore necessary to preconstrict the dural vessels with intravenously administered endothelin-1 (ET-1, 3 μg kg−1) which produced an approximate 50% reduction in dural blood vessel diameter (unpublished observations). Following administration of endothelin-1 (3 μg kg−1, i.v.) dural vasodilation was reliably evoked approximately 3 min later by intravenous rat-αCGRP (1 μg kg−1) or electrical stimulation of the cranial window (250–300 μA, 5-Hz, 1 ms for 10 s) and expressed as percentage increase in dural blood vessel diameter±s.e.mean from baseline. Rizatriptan benzoate (0.01–1 mg kg−1), PNU142,633 (0.01–1 mg kg−1) or LY334370 (3 mg kg−1) were administered intravenously 12 min before administration of ET-1 whereas human-αCGRP(8–37) (0.3 mg kg−1) was given 2 min prior to ET-1. Statistical comparisons between drug and vehicle treated rats were made by t-tests (BMDP statistical software) and P<0.05 was considered significant. [1]

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Migraine model establishment and interventions [3]
Rizatriptan benzoate control and treatment groups were intragastrically perfused with rizatriptan benzoate, 1 mg/kg per day (according to the adult daily dose), and normal control and model groups were perfused with normal saline 2 mL per day. After 7 days, nitroglycerin (10 mg/kg) was subcutaneously injected into the buttocks of the rizatriptan benzoate treatment and model groups to induce migraine. Normal saline (2 mL/kg) was injected into the normal control and rizatriptan benzoate control groups.

Absorption, Distribution and Excretion
Rizatriptan is readily absorbed (approximately 90%) following oral administration; however, the mean oral absolute bioavailability of the rizatriptan tablet is about 45%, owing to extensive first-pass metabolism. The Tmax is approximately one to 1.5 hours. The presence of a migraine headache did not appear to affect the absorption or pharmacokinetics of rizatriptan. Food has no significant effect on the bioavailability of rizatriptan but delays the time to reach peak concentration by an hour. In clinical trials, rizatriptan was administered without regard to food. The bioavailability and Cmax of rizatriptan were similar following the administration of rizatriptan tablets and rizatriptan orally disintegrating tablets. Still, the absorption rate is somewhat slower with orally disintegrating tablets, with Tmax delayed by up to 0.7 hours. The AUC of rizatriptan is approximately 30% higher in females than males. No accumulation occurred on multiple dosing.
Following oral administration of a single 10 mg of ¹⁴C-rizatriptan, the total radioactivity of the administered dose recovered over 120 hours in urine and feces was 82% and 12%, respectively. Following oral administration of 14C-rizatriptan, rizatriptan accounted for about 17% of circulating plasma radioactivity. Approximately 14% of an oral dose is excreted in urine as unchanged rizatriptan, while 51% is excreted as indole acetic acid metabolite, indicating substantial first-pass metabolism.
The mean volume of distribution is approximately 140 L in male subjects and 110 L in female subjects.
An early study involving healthy subject reported plasma clearance of 1042 mL/min in males and 821 mL/min in females; however, this difference in clearance rates is not thought to be clinically relevant.

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Metabolism / Metabolites
Rizatriptan primarily undergoes oxidative deamination mediated by monoamine oxidase-A (MAO-A) to form triazolomethyl-indole-3-acetic acid, which is not pharmacologically active. N-monodesmethyl-rizatriptan is a minor metabolite with a pharmacological activity comparable to the parent compound's. Plasma concentrations of N-monodesmethyl-rizatriptan are approximately 14% of those of the parent compound, which is eliminated at a similar rate. Other pharmacologically inactive minor metabolites include the N-oxide, the 6-hydroxy compound, and the sulfate conjugate of the 6-hydroxy metabolite.
Rizatriptan is metabolized by monoamine oxidase A isoenzyme (MAO-A) to an inactive indole acetic acid metabolite. In addition, several other inactive metabolites are formed. An active metabolite, N-monodesmethyl-rizatriptan, with pharmacological activity similar to that of the parent compound has been identified in small concentrations (14%) in the plasma.
Route of Elimination: Approximately 14% of an oral dose is excreted in urine as unchanged rizatriptan while 51% is excreted as indole acetic acid metabolite, indicating substantial first pass metabolism.
Half Life: 2-3 hours

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Biological Half-Life
The plasma half-life of rizatriptan in males and females ranges from two to three hours.

Effects During Pregnancy and Lactation
◉ Summary of Use during Lactation
Breastmilk levels of rizatriptan are low and the half-life in milk is relatively short. Amounts ingested by the infant are small and unlikely to affect the nursing infant. Painful, burning nipples and breast pain have been reported after doses of sumatriptan and other triptans. This has occasionally been accompanied by a decrease in milk production.
◉ Effects in Breastfed Infants
Relevant published information was not found as of the revision date.
◉ Effects on Lactation and Breastmilk
A review of four European adverse reaction databases found 26 reported cases of, painful, burning nipples, painful breasts, breast engorgement and/or painful milk ejection in women who took a triptan while nursing. Pain was sometimes intense and occasionally led to decreased milk production. Pain generally subsided with time as the drug was eliminated. The authors proposed that triptans may cause vasoconstriction of the arteries in the breast, nipples, and the arteries surrounding the alveoli and milk ducts, causing a painful sensation and a painful milk ejection reflex.

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Protein Binding
Rizatriptan is minimally bound (14%) to plasma proteins.

[1]. Br J Pharmacol. 2001 Aug;133(7):1029-34.

[2]. Eur J Pharmacol. 1997 Jun 5;328(1):61-4.

[3]. Neural Regen Res. 2012 Jan 15;7(2):131-5.

[4]. Brain Res. 2011 Jan 7:1367:340-6.

[5]. Brain Res. 2011 Jan 12:1368:151-8.

Rizatriptan is a member of tryptamines. It has a role as a serotonergic agonist, a vasoconstrictor agent and an anti-inflammatory drug. It is functionally related to a N,N-dimethyltryptamine.
Rizatriptan is a second-generation triptan and a selective 5-HT1B and 5-HT1D receptor agonist. Used in the treatment of migraines, rizatriptan was first approved in the US in 1998. Rizatriptan is available in oral tablets, orally disintegrating tablets (wafers), and oral film formulations.
Rizatriptan is a Serotonin-1b and Serotonin-1d Receptor Agonist. The mechanism of action of rizatriptan is as a Serotonin 1b Receptor Agonist, and Serotonin 1d Receptor Agonist.
Rizatriptan is only found in individuals that have used or taken this drug. It is a triptan drug used for the treatment of migraine headaches. It is a selective 5-hydroxytryptamine1 receptor subtype agonist.Three distinct pharmacological actions have been implicated in the antimigraine effect of the triptans: (1) stimulation of presynaptic 5-HT1D receptors, which serves to inhibit both dural vasodilation and inflammation; (2) direct inhibition of trigeminal nuclei cell excitability via 5-HT1B/1D receptor agonism in the brainstem and (3) vasoconstriction of meningeal, dural, cerebral or pial vessels as a result of vascular 5-HT1B receptor agonism.
See also: Rizatriptan Benzoate (has salt form); Rizatriptan Sulfate (has salt form).

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Drug Indication
Rizatriptan is indicated for the acute treatment of diagnosed migraine with or without aura. Rizatriptan is not indicated for the prophylactic therapy of migraine nor the treatment of cluster headache. In Canada, rizatriptan is approved in adults. In the US, the oral tablet formulations are used in patients six years of age and older and the oral film formation is approved for patients 12 years of age and older weighing 40 kg or more.
Treatment of migraine

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Mechanism of Action
There are several physiological and molecular processes implicated in the pathophysiology of migraine. Vasodilation of intracranial extracerebral blood vessels, particularly those supplying the dura mater, has been associated with migraine pain. Activation of the trigeminovascular system leads to the release of vasoactive neuropeptides (such as substance P, calcitonin gene-related peptide (CGRP), and neurokinin A) from the trigeminal nerve innervating the intracranial vessels and dura mater. Vasoactive neuropeptides cause perivascular inflammation and vasodilation in the periphery. Migraine-associated nausea and vomiting are thought to arise from the activation of central and nociceptive sensory neurons that project to autonomic brain-stem nuclei and higher subcortical and cortical pain processing centres. An imbalance in serotonin (5-HT) levels has also been documented: 5-HT binds to 5-HT_1B and 5-HT_1D receptors to promote trigeminal neuronal firing and vasoconstriction. Rizatriptan is a selective agonist at the 5-HT_1B and 5-HT_1D receptors on intracranial blood vessels and sensory nerves of the trigeminal system. It binds to these receptors with high affinity. The exact mechanism of action of rizatriptan has not been fully elucidated; however, several documented pharmacological actions of rizatriptan may contribute to its antimigraine effects. Rizatriptan causes vasoconstriction of intracranial extracerebral blood vessels, which is thought to occur primarily via 5-HT_1B receptors. Rizatriptan also inhibits nociceptive neurotransmission in trigeminal pain pathways. It attenuates the release of vasoactive neuropeptides by the trigeminal nerve, which is thought to occur via neurogenic and central 5-HT_1D receptors. Rizatriptan inhibited neurogenic dural vasodilation and plasma protein extravasation in animal studies.

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Rizatriptan benzoate is a member of tryptamines.
Rizatriptan Benzoate is the benzoate salt form of rizatriptan, a member of the triptan class agents with anti-migraine property. Rizatriptan benzoate selectively binds to and activates serotonin (5-HT) 1B receptors expressed in intracranial arteries, and to 5-HT 1D receptors located on peripheral trigeminal sensory nerve terminals in the meninges and central terminals in brain stem sensory nuclei. Receptor binding results in constriction of cranial vessels and inhibition of nociceptive transmission, thereby providing relief of migraine headaches. Rizatriptan benzoate may also relief migraine headaches by inhibition of pro-inflammatory neuropeptide release.
See also: Rizatriptan (has active moiety).

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The present studies have demonstrated that electrical stimulation of the dura mater evokes neurogenic vasodilation of preconstricted dural blood vessels in anaesthetized guinea-pigs and that the dilation is mediated by CGRP release from trigeminal fibres. In addition neurogenic, but not CGRP-evoked dural vasodilation, was also blocked by rizatriptan at clinically relevant doses via an action on presynaptic 5-HT1D receptors, since neurogenic dural vasodilation was also blocked by the 5-HT1D agonist PNU142,633 but not by the 5-HT1F agonist LY334370. The present studies suggest that the guinea-pig may be an appropriate species in which to investigate the pharmacology of neurogenic dural vasodilation providing data that can be extrapolated to man.[1]

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Opioid peptides and opioid receptor agonists exert strong analgesic effects by inhibiting neuronal pain-evoked discharges and activating the pain modulatory descending inhibitory system. Enkephalin is classified into two forms according to its structure: met-enkephalin and leu-enkephalin. They are derived from a single precursor, namely, PENK. The results of the present study revealed no significant difference in midbrain PENK expression levels between model and normal control groups, indicating that migraine does not directly influence midbrain PENK expression. However, the effects of migraine on opioid peptide expression require further study. Rizatriptan benzoate significantly reduced midbrain PENK mRNA expression, decreasing the levels of midbrain met-enkephalin and leu-enkephalin, and thereby weakening the analgesic effects of the endogenous pain modulatory system. In addition, SP has been shown to stimulate enkephalin release from the periaqueductal gray. In the present study, rizatriptan benzoate reduced SP and PENK mRNA expression in the midbrain. However, whether there is a correlation between these two reductions remains to be fully investigated. In conclusion, rizatriptan benzoate decreased expression of the mRNAs for SP and PENK in the midbrain, possibly inhibiting the analgesic effects of the endogenous pain modulatory system.[3]

C15H19N5

269.35

269.164

C, 66.89; H, 7.11; N, 26.00

144034-80-0

Rizatriptan-d6 benzoate; 1216984-85-8; 144034-80-0; 159776-67-7 (sulfate)

5078

Typically exists as solid at room temperature

1.21g/cm3

504.8ºC at 760mmHg

178-180ºC

259.1ºC

2.58E-10mmHg at 25°C

1.911

1

3

5

20

309

0

CN(C)CCC1=CNC2=C1C=C(C=C2)CN3C=NC=N3

ULFRLSNUDGIQQP-UHFFFAOYSA-N

InChI=1S/C15H19N5/c1-19(2)6-5-13-8-17-15-4-3-12(7-14(13)15)9-20-11-16-10-18-20/h3-4,7-8,10-11,17H,5-6,9H2,1-2H3

N,N-dimethyl-2-[5-(1,2,4-triazol-1-ylmethyl)-1H-indol-3-yl]ethanamine

MK-462; MK 462; 144034-80-0; MK 462 free base; 2-(5-((1H-1,2,4-Triazol-1-yl)methyl)-1H-indol-3-yl)-N,N-dimethylethanamine; rizatriptanum; 1H-Indole-3-ethanamine, N,N-dimethyl-5-(1H-1,2,4-triazol-1-ylmethyl)-; N,N-dimethyl-2-[5-(1,2,4-triazol-1-ylmethyl)-1H-indol-3-yl]ethanamine; Risatriptan; Rizatriptan

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)